﻿using System;

class NfactAndKfact
{
    static void Main()
    {
        decimal factorial = 1m;
        Console.WriteLine("Enter N:");
        decimal N = decimal.Parse(Console.ReadLine());
        Console.WriteLine("Enter K < N:");
        decimal K = decimal.Parse(Console.ReadLine());
        if (K > N)
        {
            Console.WriteLine("Invalid input!");
            
        }
        else
        {
            for (decimal i = K + 1; i <= N; i++)
            {
                factorial *= i;
            }
            Console.WriteLine("N!/K! = {0}", factorial);
        }
    }
}

